This invention relates generally to floor jacks and more particularly to a floor jack with a safety feature to prevent the jack from retracting while it is in a raised position.
The use of floor jacks is common, and various designs of floor jacks exist within the prior art. It is highly desirable to prevent such floor jacks from retracting while in a raised position, since failure of a jack in a raised position could cause great harm, possibly even fatal, to persons using such floor jacks. It is common for floor jacks to be operated by hydraulic means, and safety means are therefore highly desirable to prevent hydraulic floor jacks from retracting in the event that the hydraulics fail while a jack is in a raised position.
U.S. Pat. No. 3,783,983 discloses a safety brake system for hydraulic jack lifts such as those used to lift automobiles completely off the ground for service underneath. U.S. Pat. No. 3,759,488 discloses a rolling hydraulic jack which includes a safety means to prevent retraction of the jack shaft. This safety means comprises a propping block with a spring means for automatically forcing the block into a fixed propping position.
While the prior art discloses safety means for hydraulic jacks, there exists much room for safety improvement with hydraulic floor jacks.